In motor vehicles of the current prior art, electronic and electrical components of the motor vehicle that are especially connected with functional units of the engine compartment are housed in a so-called E-box. Such E-boxes are also generally accommodated in the motor vehicle's engine compartment. The power loss of the electronic and electrical components, such as the control units of the drive motor, the transmission control units, relays, fuses, etc. in the E-box, makes active cooling necessary in order to dissipate the heat arising due to the power loss away from the components and to prevent said components from overheating and being damaged. Up to now a fan has been provided for this purpose in or on the E-box to facilitate removal of the waste heat arising. In this case the cooling air is drawn in from the passenger footwell and the heated air is blown back into the same space. However, this embodiment of the prior art has several problems. First of all, the cooling potential is low because the intake and outlet orifices of the E-box are situated very close together. An acoustic exposure is exerted in the passenger compartment due to the connection between the motor vehicle's interior or passenger compartment and the E-box. This acoustic exposure is generated by the E-box's fan, as well as tire and engine noises which are transmitted to the passenger compartment via the E-box. Furthermore, there is an additional problem in that uncleaned cooling air, i.e. cooling air possibly loaded with dust, is drawn in from the footwell and the fan can become dirty and possibly damage the electrical components. Moreover, in the embodiment of the prior art, it is not possible to achieve any further increase in the cooling performance.
In motor vehicles there is also an increased need to cool electronic and electrical components such as control units, relays or fuses, for example, which are connected to functional units of the interior or passenger compartment, and correspondingly to dissipate the heat. These electrical and electronic components are usually installed behind the dashboard of a motor vehicle in an apparatus rack. The apparatus rack takes up a substantial amount of space behind the instrument panel or dashboard and thus also influences its design. To achieve appropriate cooling of these components, DE 697 07 663 T2, for example, disposes the electrical and electronic components in a sort of “bypass” to an existing main ventilation duct of a vehicle's climate control system. However, the “bypass” is disposed downstream of the fan and dissipates air admitted through the main ventilation duct downstream of the fan and returns said air back to the main ventilation duct downstream of the fan after cooling the components. This design causes substantial interference in the mode of operation of the vehicle's climate control system, whether it is a heating system with conventional blower or an air conditioning unit, thereby impairing their mode of operation. In addition, DE 697 07 663 T2 proposes disposing the electronics on an auxiliary ventilation duct so that cooling of heat loss producers is only possible in the dashboard, as a result of which the apparatus rack similarly requires more space in the dashboard. Furthermore, the blower in DE 697 07 663 T2 blows into the interior of the dashboard when the fan is in the ‘off’ position thus causing flow and fan noises as well as dragging in acoustic noise from the engine compartment.